Variable displacement pump control mechanism



y 1951 L. B. M. BUCHANAN 2,550,966

' VARIABLE. DISPLACEMENT PUMP CONTROL MECHANISM J Filed July 27, 1945 INVENTOR. LESLIE B. M BUCHANAN 73 14 11/. Wffh (Wig/MM ATTORNEYS Patented May 1, 1951 VARIABLE DISPLACEMENT PUMP CONTROL MECHANISM Leslie B. M. Buchanan, Springfield, Mass., as-

signor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 27, 1945, Serial No. 607,459

2 Claims.

This invention relates generally to control means and more particularly to control means for variable displacement hydraulic pumps.

Although the present invention has various applications, it is particularly adapted for use in controlling the traversing of the gun turret of a military tank by means of a hydraulic power in the pump casing in combination with a complicated system of mechanical servo linkage arranged to equalize the operation of a hydraulic control valve and to stop the cam, and therefore the slide block, in the desired position. Because of the hydraulic and mechanical connections used with this construction it has been necessary to locate the controls to be actuated by the operator in a position immediately adjacent the pump. This necessitates placing the entire pump and hydraulic mechanism in the fighting compartment of the tank turret. Since the available space in the fighting compartment of a tank turret is extremely limited, it would obviously be very desirable to be able to control the variable displacement pump by remote control means so that the pump and the hydraulic control means could be divorced from the operators control handle and located in a remote and more spacious portion of the tank, such as in the hull thereof, with only the'operators control handle remaining in the fighting compartment adjacent the operators position.

It is therefore a primary object of the present invention to provide control means for a variable displacement pump permitting the latter to be remotely operated by means of a small compact actuating unit, and enabling the bulky pump mechanism and hydraulic controls to be located remotely from the operators position. With the present invention, the remote control means comprises electrical controls which are simple in character and which may readily be connected to the pump and its hydraulically operated control means whether the latter be located in the turret off the tank or in the hull thereof.

Af'urther object of the present invention is to provide control means for a variable displacement pump in which the reaction pressure generated by the pump, when the slide block is displaced from con centric relation with respect to ill 2 the drive shaft of the pump, is counter-balanced at all times, and does not interfere with the ac.- curacy of. the control of the pump.

Other objects and advantages of the present invention will be made more apparent as this description proceeds, particularly when considered in connection with the accompanying drawings, in which:

Figure 1 is an elevation, partly in section, of a portion of the gun turret of a tank;

Figure 2 is a semi-diagrammatical cross-sectional view of the variable displacement pump. hydraulic motor, and control means for traversing th'egun. 7

Referring now to the drawing, and particularly to Figure 1, the reference character in indicates the top of the hull of a military combat tank having a turret opening I l in which is fitted and secured the usual'bearing race I2 for the turret. The turret is designated by the numeral l3 and carries a gun M, mounted upon trunnions 5 for adjustment in elevation. The turretl3 carries a complementary bearing race I6 in the form of a base ring. A set of bearings H is inserted between the two races. The lower and inner edge of the race I2 is formed as an internal ring gear 58 for a purpose which will be presently described.

Mounted upon the turret of the tank is a constant displacement traverse motor l9 which is adapted to be actuated by means of a variable displacement pump in the manner to be hereinafter described. The motor l9 operates through suitable gearing in the housing 29 to drive a pinion 2! meshing with the internal ring gear l8 fixed on the hull of the tank. The gearing in the housing 20 adapted to drive the pinion 2| is arranged to be selectively coupled either to the traverse motor is or to the manual traverse crank 22' by means of aclutch (not shown) operated by the handle 22. With this-construction the turret is normally traversed by means of the traverse motor, but in the event of failure of the hydraulic power traversing mechanism, may be manually traversed by manipulation of the crank 22' by grally with a drive shaft (not shown), the latter 7 being connected through suitable gearing to the pinion 2| ineshing with the largeinternal ring gear i8. The cylinder has a plurality of generally radially extending bores 25 in which are mounted small pistons 27. At their radially inner ends the bores 28 are adapted to communicate with ports 28 and 29 provided in the stationary fiat valve 38. The ports 28 and 25% are crescentshaped and the upper port 28 is adapted to com municate with the bores 28 of the cylinder as they pass through the arc of the upper port, whereas the lower port 29 is adapted to communicate with the bores as they pass through the arc of that port.

The roller bearing race 3| is rotatably mounted in the motor case 32 upon roller bearings 33.. The

roller bearing race 3| and the cylinder 25 are I mounted in the motor case 32 at a fixed eccentricity with respect to each other to. provide piston stroke.

Counter-clockwise rotation of the cylinder 25 and its driveshaft is accomplished when oil under pressure is furnished by the pump 23 through the conduit 34 to the upper port 28 of the flat valve 30. Port 28 communicates with the bores 2-5 to force the pistons 21 passing through the adjacent arc of the port outwardly, causing; the race 3!, cylinder 25 and drive shaft of the motor to be rotated ina counter-clockwise direction. Simultaneously, the pistons 2'! passing through the arc of the lower port 29 discharge oil through the port 29 to the conduit 35 which returns the oil to the pump 23. The pistons 21 are maintained in contact with the roller bearing race Si by centrifugal force plus hydraulic pressure.

The variable displacement pump 23 comprises a cylinder 36 formed integrally with adrive shaft (not'shown) which is driven by a suitable electric motor. The cylinder 35 is provided with a plurality of generally radially extending bores 31 in which are mounted a plurality of pistons 38. The pistons 38 are reciprocable in the cylinders and are urged by centrifugal force into engagement with a roller bearing race 39 rotatably mounted in a slide block 40 by means of roller bearings 45. The slide block 49 is mounted for sliding movement or reciprocation within the pump casing 42 upon ways provided in the casing. Ball bearings 4-4 are positioned between the ways =33 and the slide block 40.

The bores 31 and the cylinder 36 are adapted to communicate at their radially inner ends with ports 45 and 48 provided in a stationary flat valve 41.

assuming the drive shaft and cylinder to be rotated in a counter clock-wise direction by the motor, the reciprocating pistons 38 deliver oil under pressure to the lower port 45 of the flat valve 4'! as they pass through the arc of that port. The oil under pressure is delivered from the port 46 through the conduit (M to the motor liL-effecting a rotation of the cylinder and drive shaft of the motor in the manner hereinbefore described. At the same time, exhaust oil from the motor 19 is returned through the conduit 35 pressed, when assembled in the cylinder.

4 to the port 45 of the fiat valve 41 and is delivered to the bores 3'! in the cylinder 36, as they pass through the arc of the port 45.

Although a closed fluid system is thus provided between the motor is and the pump 23, there is provided a hydraulic reservoir 48 and a motordriven gear pump 49 to maintain the system completely filled with oil and to replace any leakage therefrom.

The mechanism hereinabove described is Well known in the art and is used in turret traversing mechanisms installed in combat tanks.

The present invention consists essentially in the control means for varying the position of the slide block of the variable displacement pumps, as hereinafter described.

Mounted in the pump casin 42 is a cylinder 53 having a' piston 51 reciprocable therein. The piston 5! is provided with a piston rod 52 having its forward end connected to the slide block 40. The end of the piston rod 52 is threaded and adjustably engages the slide block 40. A suitable lock-nut 53 is provided to lock the slide block and connecting rod in the adjusted position. Coil springs 5t and 55 are provided in the cylin der on opposite sides of the piston 51, and function to maintain the piston centered in the cylinder when there is no pressure difierential in the cylinder on opposite sides of the. piston. The springst i and may be preloaded, or com- When the piston 5i is thus centered, the slide block 46 is positioned. in concentric relation with the cylinder 35 of the pump.

It will be apparent that the application of fluid pressure on one side-of the piston 5| is efiective to vary the position of the slide block 40 and consequently to vary the eccentricity thereof with respect to the cylinder 36. As the aforementioned eccentricity increases, the volume of oil delivered by the variable displacement pump 23 is increased proportionately since the stroke of the pistons 38 is greater. In a like manner the speed of the motor i9 is dependent upon the volume of oil delivered by the pump. Reversing the eccentricity of the slide-block 49 with respect to the cylinder 36 reverses the flow of oil through the pump and results in reversing the direction of rotation of the motor l9. Thus it will be seen that the speed of the motor IS, and accordingly the speed of rotation of the turret E3 in either direction, is accurately controlled by varying the position of the slide block 40 by means of the application of fluid pressure in the cylinder 50.

24 is an electro-magn-etic valve arranged to control the flow of fluid through the conduits 56 and 51 to the cylinder 50 on opposite sides of the piston '51. The electro-magnetic valve 24 may be built as part of the pump 23, or may be a separate unitv connected to the pump by the conduits 56 and 51, as shown. The motor driven gear pump 58 provides fluid under pressure to the. conduits 56 and 51. By-pass conduits 59 and 6B establish communication between the conduits 56 and 51 and the fluid pressure valves 6| and 62 respectively. The valves 6| and 552 have exhaust ports respectively controlled by plungers 63 and 64. These plungers are arranged to be reciprocated by the magnet bar 65 which is pivoted intermediate its end upon the fulcrum 66. Magnet coils 6'! and B8 are wound upon cores 69 and 19 respectively and are adapted to be energized to pivot the magnet bar 65 about the fulcrum. 66-,

- thus moving the plungers 63 and 64 to open one of the-pressure valves and simultaneously close the other." f i "ifOneend of each coil fil and 68 is grounded at 7| and the opposite ends are. connected tothe center terminals of a double-pole, double-throw switch 13. The switch is adapted to connect the coils to either of two potentiometers l4 and I5. The potentiometers T4 and are provided with manual controls 16 and 71, which may be operated to vary the electrical power supplied to the coils 61 and 68 from the power source 18.

It will be seen that operation of the potentiometers connected by the switch 13 to the magnet coils B1 and 68 increases the energy suppliedto one coil and simultaneously decreases that supplied to the, other, resultingin rocking the magnet bar 65 about its fulcrum 66. In thismanner, one of the plungers '63 and M is movedtoward its adjacent pressure valve and restricts the port or orifice thereof while the other plunger moves away from its adjacent pressure valve and opens the'orifice thereof. The orifices of the pressure valves El and t2 provide in effect means for bypassing the fluid supplied to the conduits 56 and 51 from'the gear pump 58, and regulation ofthe size of the orifices by the plungers 63 and 64 results in increasing the pressure to one side of the "piston 5| in the cylinder 50 and simultaneously decreasing the pressure supplied to the opposite side of the piston. In this manner controlled reciprocation of the piston 5| and the 40 connected thereto is secured;

The springs 54 and 55 in the cylinder 50 on opposite sides of the piston 5| oppose movement of the piston by the difierential pressure in the conduits 56 and 51 and function to measure the movement of the pistons and to control the movement thereof in accordance with the amount of power supplied at the potentiometers. In other words, a definite position of the piston 5| and accordingly the slide block 40 is obtained for each electro-magnetic valve may be positioned in any suitable location in the tank, and the controlling potentiometers maybe located in the fighting compartment of the tank turret adjacent the operators position. Since the potentiometer controls are small and compact it is apparent that they occupy little space and may be conveniently located in the turret. On the other hand, pump and electro-magnetic valve are relatively large and when located in the limited space provided in the fighting compartment of the tank turret are in the way and impair the efiiciency and free movement of the personnel stationed therein. Furthermore they obstruct the efiicient location and arrangement of other apparatus in the turret. By remotely locating the traversing mechanism from the controls, a more eficient interior arrangement of the tank is possible.

The use of two potentiometers l4 and 15, as shown in Figure 2, enables the traversing mechanism to be controlled by either of two operators at two separate stations, simply by operating the switch 13 to connect the magnet coils 6i and 68 to the potentiometer at the desired station. If desired, of course, only one potentiometer is necslide block essary if, the traversing mechanism is to be con trolled and operated from a single station:

An inherent characteristic of variable displacement pumps of the type illustrated and described is that movement of the slide block to an eccentric position with respect to the cylinder and drive shaft thereof produces a reaction force within the pump, tending to return the slid block to concentric relation with the cylinder and drive shaft. In the construction shown in Figure 2, means are provided for counter-balancing this reaction pressure generated by the pumpso that it will not interfere with the accurate operation of the traversing mechanism. A cylinder 80 is provided as an extension of the cylinder 5|] and receives a piston 8| mounted for reciprocation therein. The piston 3| in the cylinder 80 is con nected to the piston 5| in the cylinder 50 by means of the connecting rod 82, for reciprocation therewith as a unit. A guide rod 83 of the same diameter as the connecting rod 82, extends from the opposite side of the piston 8| and is received in a guide bore -84 provided in an extension 85 of the cylinder 56. The conduit 34 from the variable displacement pump 23 communicates with the cylinder 80 on one side of the piston 8| by means of the conduit 86, and the conduit 35 from the pump communicates with the cylinder 89 on the opposite side of the piston 8| by means of the conduit 87. The piston 8| is of such diameter that the reaction force of the variable displacement pump 23 tending to return the slide block to concentric relation with the drive shaft the conduit 34 to the motor I9 and is also supplied to the right side of the piston 8| by means of a conduit 85. In this manner the output oil pressure from the pump tends to move the small piston 8| to the left, and inasmuch as this piston is connected by the connecting rod 82, piston 5| and connecting rod 52 to the slide block 4|], it will be apparent that the reaction force tending to move the slide block to the right is counterbalanced. The reaction force generated in the pump when the slide-block is displaced to the right from its position shown in Figure 2, is similarly counter-balanced by means of the output oil pressure from the conduit 35 being applied on the left side of the piston 8| through the conduit 81, thus counter-balancing a reaction pressure in the pump.

Since the reaction pressure in the pump tend ing to return the slide block to its neutral position is a function of the output pressure, the reaction force will be increased as the displacement is increased and as the output pressure is increased. Since, however, the output pressure acts directly upon the piston 8|, the reaction pressure in the pump is always counter-balanced by the small piston 8 I. Accordingly, when an increase is required in the torque necessary to rotate the turret, the pump output pressure is increased, but the increased reaction forcein the pump is counter-balanced by the increased counter-balancing force of the piston 8|; J

Although I have shown and described certain embodiments of the invention, it will be'understood that I do not wish to be limited to the exact construction shown and described, but that various changes and modifications may be made Without departing from the spirit and scope of my invention, as provided in the appended claims.

What I claim is: I

1. In a closed fluid power transmission system of the character described wherein a pair of fluid conduits for delivery and return fiuid flow are connected to respective ports of a variable displacement hydraulic pump having a slide block which is movable to vary displacement of the pump, pump displacement control mechanism comprising, in combination, a pair of cylinders arranged together in tandem, a pair of pistons rigidly connected to each other and movable as a unit Within said cylinders, each of said pair of pistons being within a respective one of said pair of cylinders, means rigidly connecting said connected pair of pistons to said slide block for unitary movement with the latter, means establisning fluid communication between said pair or fluid conduits and one of said cylinders at respective opposite sides of the one of said pis tons therein, whereby reaction force of said slide block during operation of said pump is counterbalanced by fluid pressure acting on said one of said pistons, a source of fluid pressure, a pair of fluid pressure conduits connecting said source of fluid pressure to the other of said cylinders at respective opposite sides of the said piston therein, a pair of valves for selectively regulating fluid pressure in respective ones of said pair of fluid pressure conduits, electro-magnetic means for controlling said pair of valves;

and manually Operable electric control means for variably regulating said electro-magnetic means.

2. In a closed fluid power transmission system of the character described wherein a pair of fluid condiuts for reversible delivery and return fluid flow are connected to respective ports of a variable displacement hydraulic pump having a slide block which is movable to vary displacement of the pump, pump displacement control mechanism comprising, in combination, a pair of abuttingcylinders arranged with their hori-- zontal axes in alignment, a piston in each of said cylinders, a connecting rod rigidly connecting the piston in one of said cylinders to the piston in the other of said cylinders, a rod rigidly connecting said connected pistons and said connecting rod to said slide block for movement as a unit with the latter, .a pair of connectionsestablishingfiuid communication between said pair of fluid conduits andone of said cylinders at respective opposite sides of said piston therein, whereby reaction force of said slide block during operation of said pump is counter-balanced by fluid pressure acting on said piston in said one of said cylinders, a source of fluid pressure, a pair of connecting conduits establishing fluid communication between said source of fluid pressure and the other of said cylinders at respective opposite sides of said piston therein, a pair of valves for selectively regulating fluid pressure in respective ones of said pair of connecting conduits, and manually operable electric control means for variably regulating operation. of said valves.

LESLIE B. M. BUCHANAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,902,063 Ferris, et al Mar. 21, 1933 2,027,104 Kahr, et a1 Jan. 7, 1936 2,177,098 Doe, et a1. Oct. 24, 1939 2,263,314 Rose Nov. 18, 1941 2,302,922 Tucker Nov. 24, 1942 2,381,160 Hanna Aug. 7, 1945 2,385,069 Ferris Sept. 18, 1945 

